Experimental and computational fluid dynamic (CFD) studies on mixing characteristics of a modified helical ribbon impeller

Abstract

Experimental and computational fluid dynamic (CFD) modeling studies have been performed on mixing characteristics of a new modified helical ribbon impeller in a viscous medium. A novel arrangement for the multiple reference frame (MRF) technique was proposed and the modeling results were compared with those of conventional MRF selecting method. Calculations were performed to study the effects of several parameters: axial flow number, axial circulation time, impeller clearance, and power consumption. The higher performance of the modified impeller has been proven in terms of axial flow number and axial circulation time. The results showed that significant improvement in mixing performance can be obtained at a higher impeller clearance with the modified impeller employed. In addition, the power consumption by the new impeller has been compared with that of the classic one. The CFDpredicted flow patterns generated by the impellers were used to explain the higher performance of the modified impeller. In addition, the results reveal that the CFD-predicted particle volume fractions at various axial distances from the tank bottom are reasonably in agreement with the experimental observations.

Flow Characteristics in Mixers Agitated by Helical Ribbon Blade Impeller

“…Therefore, multiple frames are adopted in our calculations. The multiframe of reference has also been adopted by Rahimi et al (2010) in calculating the flow in helical ribbon impeller mixers. As shown in Fig.…”

“…Good agreements with experiments were reported in terms of the circulation time and torque. This method was also used to model the mixing flow of second-order fluids stirred by a helical ribbon Rahimi et al (2010). It was shown that after modifying a helical ribbon impeller by placing two 45 0 flat blades on the bars connecting the ribbon blade and the shaft, the mixing performance is improved with a negligible increase in power consumption.…”

Effect of the Rotating Reference Frame Size for Simulating a Mixing Straight-Blade Impeller in a Baffled Stirred Tank.

“…It has been reported that both results are comparable (Wechsler et al, 1999). MRF modeling has been intensively used in CFD simulations of stirred tanks operating at different flow regimes regimes (Deglon and Meyer, 2006;Glover and Fitzpatrick, 2007;Rahimi et al, 2010;Ammar et al, 2012;Sossa-Echeverria and Taghipour, 2012;Chtourou et al, 2014;Raffo-Durán et al, 2014;Devi et al, 2015;Ramírez-Gómez et al, 2015;Ramírez-Muñoz et al, 2016).…”

Chaotic mixing in a barrier‐embedded partitioned pipe mixer

“…Based on the means used to induce mixing, mixers are classified into two categories: dynamic mixers and static mixers . Dynamic mixers exploit moving parts or externally applied energy such as acoustic, thermal, and electrohydrodynamic energy, while static mixers are motionless mixers, independent of external means other than pumping power (e.g., lamination, interdigital, and the split‐and‐recombine concept). Dynamic mixers inevitably require complex structures and fabrication processes to employ the components for the energy sources and input, which leads to expensive manufacturing and maintenance costs.…”